The final DJ quest now requires you to have an empty inventory slot.

If you have finished the quest while your inventory was full and didn't get the reward, the item will be automatically granted to your inventory when you enter the game after this update. If your inventory is currently full, the game will wait until there's a space to give you the item. You can get in the game, empty a slot in your inventory, go back to the main menu, and enter the game again, and you should have the item.